A. Field of Invention
This invention pertains to an air bag passenger restraint system, and more particularly to a housing for the components used to inflate the air bag in such a system.
B. Description of the Prior Art
Active passenger restraint systems and more particularly, restraint systems with air bags have proved to be very effective in preventing serious injury and even death in motor vehicles involved in crashes. Typically, these systems include an inflator housing containing chemical agents which may be triggered, for example by a crash, to generate a large volume of gas. The housing is arranged and constructed so that the gas is channeled to a bag which inflates. Thus, the big cushions the body of the passengers.
Early gas generator or inflator designs comprised two metal cups which were held together on their circumference to form a pressure chamber. As pressures typically reach 2000 psi within a gas generator, the wall thickness of these cups had to be sufficient to withstand this pressure typically with a safety factor of 2. These cups were typically held together by welding, threads, or by mechanically bending one cup around the other.
In an effort to reduce the overall weight of the gas generator by reducing the wall thickness of the cups, means were sought to provide a physical attachment of the two cup halves at some inner diameter. In one prior art configuration, in addition to the peripheral attachment, an inner bolt circle of rivets was used to provide this additional attachment as well as a separate two-piece threaded member that served both to hold the electric squib as well as provide mechanical attachment of the upper and lower half. The outer periphery of this type of inflator was welded.
Another configuration utilized a butt welding technique wherein the two cup halves were friction-welded together at both the peripheral diameter as well as an inner diameter. Yet other configurations utilized several interconnecting cup members which were laser or electron-beam welded together to form the desired multi-attachments of the gas generator pressure chamber. Some prior art inflator housings are shown in U.S. Pat. No. 4,711,466; and 4,561,675. However, it has been found that assembling inflator housings by welding is undesirable because it increases their cost of manufacture and weight. Moreover, in some instances it may be advantageous to be able to disassemble a completed housing, for example for quality control, or to replace defective or old chemical agents. However, a welded housing is difficult to take apart.